1. Field of the Invention
The present invention relates to novel polydiorganosiloxane/thiuram disulfide block copolymers, to a process for the preparation thereof, and to the use of such novel block copolymers in the radical polymerization of vinyl monomers to produce characteristic polydiorganosiloxane/polyvinyl block copolymers.
This invention especially relates to the industrial-scale production, strictly by radical polymerization process, of polydiorganosiloxane/polyvinyl block copolymers having a polydiorganosiloxane block at each end of the polymer chains.
2. Description of the Prior Art
The journal article, Makromol. Chem. Rapid. Commun., 3, 127-132 (1982) describes the use of tetraalkylthiuram as an additive during the radical polymerization of vinyl monomers, such additives being designated an "iniferter" because during this polymerization it performs the triple function of free radical initiator, chain transfer agent and chain terminating agent.
The journal articles, Polymer, 29, 1909-1917, (1988) and J. Macromol. Sci.-Chem., A 25(9), 1089-1126 (1988) described polymeric "iniferters" based on poly(thiuram disulfide) bearing polyphosphonamide blocks.
These polymeric "iniferters", hereinafter deemed "polyiniferters", are prepared by the preliminary synthesis of a macrodiamine obtained, for example, by reacting the dichloride of phenylphosphonic acid with piperazine or N,N'-dimethyl-1,6-hexanediamine. The chain extension of this macrodiamine by a dithiocarbamylation reaction, followed by an oxidative coupling, gives a poly(thiuram disulfide) bearing the phosphonamide functional group. Thermal radical polymerization of methyl methacrylate or styrene in the presence of these "polyiniferters" results in the formation of polyvinyl/polyphosphonamide block copolymer.